Head gaskets employing laminated bodies with U-shaped armors at the combustion openings produce consistently effective seals, both for conventional automotive engines and diesel engines. Occasionally, however, the configuration of the engine or the location of precombustion chambers in diesel engines are such that they produce localized zones of exceedingly high stress which so deform the gasket in use that under some operating conditions, the gasket will fail to seal consistently and in an effective manner.
A typical such gasket which encounters sealing difficulties under some circumstances is one in which the precombustion chambers of two adjacent cylinders are closely adjacent to each other, thereby producing an abnormally high local temperature. The high temperature tends to cause the engine head to deform and distort non-uniformly, resulting in abnormal local loads at the armors. This so-called "thermal push" causes the armors to stress more in that local area than elsewhere. Thus, the armor is distorted and the underlying facing layer of the laminate is likewise distorted. The net result is that the zone of the armor which is excessively distorted will not recover sufficiently to provide an effective seal at the time of engine start-up. That being so, gases will escape and power will be lost.
It would be desirable to eliminate the deleterious effects of thermal-push in zones of close adjacency of precombustion chambers.